1. Field of the Invention
The present invention relates to an automatic quality judgement apparatus and judgement method for lamps such as incandescent lamps, etc. More particularly, the invention relates to an automatic judgement apparatus and a judgement method in which the quality of a lamp is judged by detecting the state of gas that is sealed in the lamp.
2. Discussion of Background
Recent years have seen the development of high-speed automated lamp manufacturing equipment for automatic mass-production of a variety of types of lamps. In such a manufacturing process, in the case of incandescent lamps, for example, if evacuation of air is not effected satisfactorily in the course of the process or if the purity of the gas that has an inert gas such as Argon, etc. as its main component and is sealed in a lamp is low or if the sealing is unsatisfactory and slow leakage occurs, the filament breaks after only a short time of use (the life of the incandescent lamp becomes short) or there is reduction of the flux when the lamp emits light or there is deterioration of the flux maintenance characteristic, with the emitted light flux falling with elapse of light emission time. When such undesirable, defective lamps are manufactured, the defective products must be picked out and removed prior to shipment to the market.
There have been developed devices and methods for detecting the quality of incandescent lamps, i.e., for detecting whether or not admixture of air or moisture, etc. as well as Argon and Nitrogen gas has occurred due to improper sealing, without breaking the lamps.
For example, in a procedure conventionally employed in lamp manufacturing works to detect the state of gas in lamps and remove undesirable lamps during the lamp manufacturing process, a high frequency voltage is imposed on all the incandescent lamps that are manufactured to cause production of a discharge in the lamps and an operator removes lamps making a visual judgement of the color of the emitted light resulting from this discharge, so preventing shipment of the undesirable, defective incandescent lamps to the market.
FIG. 15 shows an example of conventional operator-sorting. The high frequency voltage of a high frequency voltage generator 1 is supplied by a lead wire 2 to a discharge terminal 3, whereupon a high frequency discharge is produced between discharge terminal 3 and a filament or similar metal element not shown that is inside an incandescent lamp 4. The operator ascertains the state of the gas in incandescent lamp 4 and judges the quality of the product by observing, with the naked eye 6, the color of the radiated light and the form of the discharge at this time.
However, there has been a sharp increase in operators' wages and incandescent lamp manufacture has suddenly become a high-speed process recently, making it impossible for operators to keep up with the production speed by naked eye judgements as in this conventional procedure, and in view of these and similar factors there have been attempts to automate inspection.
An example of an automatic classification device is shown in FIG. 16. This is a device in which a sensor device 10 judges the light that is emitted when discharge occurs between the filament or other metal element inside an incandescent lamp 9 and a discharge terminal on which the high frequency voltage of a high frequency voltage generator 7 has been imposed. Sensor device 10 consists of a filter 11, photoelectric tube 12 and metering relay 13. When the discharge occurs, light, e.g., 360-420 nm light, which has passed through filter 11 is converted to a photoelectric current by photoelectric tube 12 and the voltage produced by causing this current to flow through a set load is supplied to metering relay 13. Incandescent lamps 9 for which the voltage is within a set range that has beeb set for metering relay 13 are taken to be passes and are forwarded to the next stage 14, while defective incandescent lamps 9 for which the voltage is outside this range are sent as rejects to a reject section 15.
In a conventional example such as this, however, there is the problem that it is difficult to detect whether products are good or not with a set filter for, e.g., 360-420 nm, because the discharge generation conditions vary.
A known example of a device such as this is that disclosed in Japanese Utility Model Disclosure No. 56-117465.
In more detail, a discharge terminal is brought near the outer wall of an incandescent lamp's bulb, glow discharge between the lamp's filament and the discharge terminal is produced by a high frequency voltage and the state of the sealed-in gas is judged on the basis of this glow discharge. Further, the quality of the lamp is determined through detection of the intensity of that portion of the light of the glow that is in the wavelength region 360-420nm.
With this technique, the quality of a lamp is judged on the basis of that light in the light spectrum produced by discharge which is in a wavelength region in which the intensity of the light varies in correspondence to the degree of defectiveness of the lamp, and the technique has the desirable aspect that the related configuration is made simple.
However, there is the drawback that reliable judgement is not possible, because the intensity in a specific light spectrum is detected and if, for example, the discharge inside lamps becomes unstable, this inevitably leads to a change in the light spectrum. Although it is desired to have a technical means for eliminating this drawback, all conventional techniques used judge lamp quality on the basis of intensity in a specific light spectrum and were therefore subject, in no small way, to adverse effects accompanying slight changes in the discharge phenomenon.
In view of this, the present inventors earlier developed an automatic incandescent lamp classification apparatus (Japanese Patent Application No. 60-167394) as follows.
It having been noted that although levels in a set wavelength region in the light spectrum produced accompanying incandescent lamp discharge when products are good are markedly different from the levels when products are deflective, the ratio of the intensity of light in this set wavelength region and the intensity of light in another region is practically unaffected and remains generally constant even if changes in level occur and can give improved classification performance, the apparatus uses the intensity ratio of the light in these two regions to judge the quality of incandescent lamps.
In the meantime, there has come to be a demand for still greater improvement of the classification performance of this apparatus, since today incandescent lamps are required to have extremely high reliability.